There are many reasons why a homeowner should waterproof their basement that go beyond the fact that a damp or wet basement is uncomfortable and fairly unusable. A damp basement is the perfect growing environment for molds and fungi, which can badly affect pets and people who are allergic to them. Damp basements can also cause paint to peel and can rot wood. They can also warp walls, especially drywall, as well as floors and ceilings.

The best way to waterproof a basement is to install good draining around the entire house and make sure that soil slopes away from the house’s perimeter. The soil should slope at least 6 vertical inches in the first 10 horizontal feet from the foundation wall. It also helps to control water runoff from the roof and the outside wall. Good drainage will be further helped if the homeowner or contractor places 1/2 inch of cement or parging masonry on the outside basement walls, then two coats of a sealant made of bituminous tar.

Another good drainage system will also direct the water from the foundation toward the house’s footing. This is where the drainage tiles or draining pipes can collect the water and take it away from the house, or collect the water and discharge it from a sump pump. For these drainage lines to work well they’ll need to be embedded securely in a porous substance like gravel.

Downspouts should be connected to horizontal and gently sloped pipes that also carry the water away from the foundation. If there’s a pavement in the way, drain tile can draw the water beneath it to open ground or a catch basin. If a catch basin is being used that will then empty into a drain pipe, the catch basin should be far enough from the foundation to make sure that the runoff won’t overshoot it during a downpour, but close enough to catch the flow during a light rain. The water can also flow into a dry well where the water drains away or sinks into the ground. A dry well should also be built well away from the drip line of a large tree, because the soil can be saturated to the point where the tree can be destabilized and fall over in a strong wind. Not only would the tree fall down, but the roots would also be torn up.

Sometimes the building will need to be level and there can’t be any drainage slope away from it. In that case a trunk and arm drainage system can be installed. Perforated drain tile acts as the trunk and runs parallel to the foundation. Solid drain tile can be the arms, which are fastened to the trunk with T connectors. These tiles are perpendicular to the trunk and about ten feet apart. They slope underground to dry wells filled with gravel. This will allow the dry wells to collect the runoff water, which will eventually sink into the earth.

Granted, these drainage systems may be expensive and time consuming to install, but they’re certainly no more costly than the possible consequences of a basement that’s allowed to stay wet or damp for years.